Converter OUTPUT to solar charger INPUT?

[gordon2]

This topic is an offshoot of this thread.

Originally Posted by redbarron55

I like the trimetric, but it is a little pricey if you don't have a solar system.
I talked with the guy about the charging controller if it could be used with a regular battery converter that might be regulated to a higher voltage to mimic a solar setup.
He said is should work just fine, but he had not tried it.....

What guy?

I have given this just enough thought to be dangerous

My solar system is the Bogart Engineering SC-2030 with the sibling TriMetric meter. The solar charger is a better charger than the PD converter, even with the "Charge Wizard" add-on. One reason that I believe this is that the solar system with the TriMetric shows the amount of charge and it stops at 120% which is the amount of overcharge programmed in at present to account for charging inefficiencies (and then maintains the battery in float mode). The solar charger also has a temperature sensor on the battery and the converter has no method to do temperature based adjustment to it's charging profile.

However, without the solar system, the TriMetric tracks the charging from the converter / charge wizard alone, and it goes past 120%. The last time I used the converter it was at 199% before I shut off the converter. So it appears that the converter will overcharge even with the Charge Wizard which is supposed to turn the converter into a "Smart Charger."

If I wired the converter output (without the Charge Wizard) to the solar charger input then it would in effect act as just another solar panel (wired in parallel), and the charging would always be controlled by the controller (duh!) instead of the converter (when on shore power).

So I am wondering if there is any downside to this idea and what circuit protection would be appropriate. And, if the converter and solar panel(s) are mismatched in voltage, how much of a mismatch is OK? Apparently the converter output is fixed at 13.6 VDC and not adjustable. Like I said, I have only thought about it enough to be dangerous so further research is called for. If this is a good idea, surly someone has done it already.

[Franswa]

what you propose seems logical...but that's no guarantee it'll work.... given how "murky" the 12V world is....

when my converter/charger failed....the questions you pose is what led me to get rid of the whole thing (IMO the lazy man's way of running the electrical system in an RV)....install the best/smartest charger I could find....and lastly wire the system so I can isolate it's components (charger and solar power)

what I found lately might be of interest....

"Handy Bob" states that most chargers and controllers, out of the box, cannot deliver a high enough voltage (in the 14.5 range) to FULLY charge a battery bank. In his opinion, these chargers/controllers can only charge a battery bank up to 80% capacity even though the bank at rest will give you a voltage reading of 12.65+....

in my case, with my trailer parked in the backyard, with 70W of solar on the roof...after days of bright sunshine the voltmeter reads 13.3V (maintenance charge)....if I shut the panels off and then turn my charger on....after the initial minute or two (battery bank assessment according to the owner's manual) the voltage starts to rise and eventually reads 14.5 or 6......and it remains there for the next 24 hours or so before dropping back down to 13.3 to 6 which I assume is the charger's maintenance charge after it reads the battery bank as "fully charged"...

a hydrometer test sort of confirms the above.....after a routine "full" solar charge the hydrometer reading is at or above 1.265...(in the "green" zone).......after a "full charge" from the charger as described above, the hydrometer reading is right off the scale !!!! (past the green zone!)

just what is happening with me.....thought it might be of interest

good luck and I hope you report back on what you find out while experimenting further....cheers, F

[gordon2]

Originally Posted by Franswa

...
"Handy Bob" states that most chargers and controllers, out of the box, cannot deliver a high enough voltage (in the 14.5 range) to FULLY charge a battery bank. ...

Indeed what you and HandyBob point out is (IMHO) even more argument to use the SC-2030 as the charge controller for both solar and the onboard converter (and most other chargers), at least if one does not have a top notch charger.

The TriMetric and SC-2030 combo allows full programmatic control of the charging profile. The standard profile for generic wet cells (shown below) has the absorb voltage set to 14.4 (and you can set it to 14.5 if you like).

Now of course the solar charge controller will not increase the voltage from the converter, so a full charge will either require the use of solar panel(s) which output a higher voltage or increasing the voltage coming from the converter. I said above that the converter (PD-9100 series) apparently has a fixed voltage of 13.6 volts however the “Charge Wizard” varies the voltage depending on its assessment of the battery’s condition of charge. It has four modes:

1. Normal, 13.6 volts
2. Boost, 14.4 volts
3. Storage, 13.2 volts (activated by no battery activity for 30 hours)
4. Desulfation, 14.4 volts for 15 minutes (every 21 hours when in storage mode)

How the PD-9100 with charge wizard would interact with the solar controller is a mystery to me. If it were to sense the higher voltage from the solar panel then that might have an effect on the charge wizard’s operation but my best guess is that it would not be a problem.

It would be simple if one could just increase the voltage from the converter from 13.6 to 14.4 (the same as the Charge Wizard boost mode). The Charge Wizard would then be unneeded as the solar controller would in effect take it's place. However I am not willing to make any internal changes to the converter to bump up the voltage, if for no other reason than it would be a problem for the next owner.

The Charge Wizard’s mode can be manually selected by the user pressing a button on the device, so perhaps there is a way to use the TCMS port on the converter (which is the port the Charge Wizard uses), to trick the converter into staying in boost mode. Then the SC-2030 solar controller would be supplied with 14.4 volts (or more if from solar), and it would do all the regulating and charging according to its programmed profile.

Sample charging profile from SC-2030 Solar Controller manual:



P1: Absorb volts: When charging begins, the maximum solar current is sent to the batteries until this voltage is reached. Then the charger limits voltage to this value. (10.0-65.0)
P2: Charged setpoint. Amps value, expressed as a percentage of P3: from 0.0-10.0%. When the amps drops to this value with voltage equal or just greater than P1, and the TM-2030 is in Levels 1-3, the batteries are signaled as "charged." (In Level 4, the standard is much higher: batteries must go into float mode before they are signaled as “charged”.)
P3: Total battery system capacity (in amp hours). (10-10,000 amp hours)
P14: Limit timer for charging, before going into "Float" described in the profile graphs. (0.0-25.0 hours)
P15: Finish charge (high) voltage limit—allowed only after the amps drop below the P21 current limit. (10.0-65.0)
P16: Float voltage (10.0-65.0)
P20: Percent of overcharge before going into "float" (0-20%).
P21: Finish charge Amps limit (expressed as a percentage of P3) below which amps must be to rise to P15 voltage.

[Franswa]

you sort of confirmed my suspicion that the weak link in my system is my cheap or unsophisticated (you pick) solar charge controller...it's a generic contoller meant to charge a battery and run a set of lights(probably) off-grid somewhere

at the moment I am content to "manually" run/monitor my system with what I've got....it seems to perform well enough for my use that is usually 2-3 days off-grid and then pull into a full service campground or go home (where I can plug the charger back in). I have read that it is advisable to not let the bank go down below 12.4 to acheive maximum battery life and that is what I am roughly seeing off-grid... with a certain amount of sunlight....(my power needs are quite small...no TV or coffee maker....just LED lights, boom box, water pump and fridge controller) as an aside I plugged in my "low on battery power" laptop the other day and was surprised at how much power that draws!!!

You on the other hand, if I'm reading this right, are trying to "marry" your superior controller to your charger/converter so that your whole system is on "auto-pilot"...requiring no input from yourself once you have it all set up....a worthwhile endeavour I would think...certainly a fun "puzzle" to play with...as is all this 12V stuff
good luck... sorry I can't be of much help in that regard

for reference my system is
2x GC batteries
70w of solar flat on the roof + 40W deployable
one cheap solar charge controller
one very smart charger (7.2A, double insulated, no fan)

[Byron Kinnaman]

My guess is you don't need the converter. The solar panel will take care of your charging needs, therefore you can turn the converter off and not worry about it.

[gordon2]

Originally Posted by Byron Kinnaman

My guess is you don't need the converter. The solar panel will take care of your charging needs, therefore you can turn the converter off and not worry about it.

In fact the converter does stay turned off most of the time, but sometimes I just don't feel like lugging out the bulky panel, or leaving it outside at home all the time where it would become a tempting theft target. If I only need to run a wire from the converter to the controller to get improved charging the rest of the time, along with a longer battery life and a better charged battery, it sounds like a good plan to me.

[Byron Kinnaman]

Originally Posted by gordon2

In fact the converter does stay turned off most of the time, but sometimes I just don't feel like lugging out the bulky panel, or leaving it outside at home all the time where it would become a tempting theft target. If I only need to run a wire from the converter to the controller to get improved charging the rest of the time, along with a longer battery life and a better charged battery, it sounds like a good plan to me.

I can tell what I've done. My converter never runs. I bought a Battery Minder, or Battery Tender use that while at home. That way the battery stays topped off without a lot of over charging. I get a desulfate cycle ever once in a while.

To make it easier I added a cable with a connector on the end and the mating connector on Battery Minder cable. When not in use I simply shove the connector into the battery box. This makes it easy to attach and disconnect. It's also the same connector I use for the solar panel. FYI I have the solar charge controller mounted on the solar panel. My solar panel charges the house batter plus a ham radio battery.

Good luck with your endeavors.

[Timber Wolf]

Interesting thread. I installed a Trimetric last year to monitor my new batteries. I already had another brand solar controller so put off buying an SC-2030 till this year, it and the temp probe sit in a box on my dining room table as we speak. I also did a converter upgrade last year (or was it the year before?) to a new PD with charge wizard. I have been happy with it although I have not done a careful analysis as Gordon has done. I don't think I will bother routing the PD output through the SC-2030 but leave them both as stand alone systems. I usually do not plug in at home any more anyway until just before leaving on a trip to cool down the Truckfridge. I am not worried about theft and one 100W panel (even though poorly oriented) recharges and seems to maintain my two 6V batteries fine. That is the thing about solar, it is relentless. If the sun is shining you be charging. I expect even better performance out of my solar set-up after installing the SC-2030. I need to get that done ahead of this Fall/Winter's boondocking!

[gordon2]

A little more digging around the net yielded this link that gives me an idea.

The above link documents a modification to the PD9100 Charge Wizard to vary the voltage output, but the author mentions that you can get a fixed voltage of about 17 volts simply by grounding one wire. If he is right, and if this does not damage the converter, then it would be easy to bump up the voltage output from the converter to a level that would be good for the solar controller to utilize.

Just thinking about this for now and discussing it here. Nothing herein is endorsed by me. The idea is to disconnect the output wires currently on the converter, ground the green wire and verify voltage is around 17, and run new wiring from converter output straight to the the solar controller input in parallel with the solar panel(s). Fuses would be added in case the current form multiple sources becomes too high.

[gordon2]

and even more digging results in finding this thread.
Post # 9 explains why this might be a bad idea.

And this thread tells the story of someone who tried this very idea and blames it for the death of his converter.

So, while I think it would be easy to get the higher voltage from the PD9100 series converter, it might be a bad idea to use the converter in lieu of a solar panel as a solar controller input.

[Larry,C]

I came across this diagram in a manual for a popular solar controller. Note the comment regarding connecting the converter.

[Byron Kinnaman]

Originally Posted by Larry,C

I came across this diagram in a manual for a popular solar controller. Note the comment regarding connecting the converter.

There's a great big yabut in this. Solar or no solar doesn't matter when you create that kind of loop you're going to run the battery down. There's been a couple people try the loop, it simply can't work. No perpetual motion machine, always losses.

As far as running the output of the converter to solar controller. I suppose it could be done with a lot of work and thought, but why? All you need to do is connect any and all charging devices to the battery. Each charging device, converter, solar, tow, etc.etc.etc. will each work as needed. It's really that simple.

[Larry,C]

Originally Posted by Byron Kinnaman

There's a great big yabut in this. Solar or no solar doesn't matter when you create that kind of loop you're going to run the battery down. There's been a couple people try the loop, it simply can't work. No perpetual motion machine, always losses.

As far as running the output of the converter to solar controller. I suppose it could be done with a lot of work and thought, but why? All you need to do is connect any and all charging devices to the battery. Each charging device, converter, solar, tow, etc.etc.etc. will each work as needed. It's really that simple.

Not sure I get the "yabut" You are agreeing with the note that I was pointing out.

Personally I avoid the whole problem by putting enough solar on the roof so I don't need a converter. I disconnected mine and my solar panels have been caring for my batteries for the last 3 years.

[Larry,C]

Maybe you need to look at the diagram and the note. I don't know what you are talking about.

[Larry,C]

I'm pretty sure we all agree that the perpetual machine won't work. The point of the diagram and note that I posted was to give a good reason why it wouldn't work.

[Larry,C]

The note says “If the inverter supplies power to the AC panel which in turn provide power to a converter, the resulting battery loop will quickly drain the batteries" I thought that was enough detail

[gordon2]

Originally Posted by Larry,C

I'm pretty sure we all agree that the perpetual machine won't work. The point of the diagram and note that I posted was to give a good reason why it wouldn't work.

Your diagram is not germane to the question I posed in this thread. In my proposal, there is no inverter at all. There is no loop created.

The idea is to route the 12 volts DC from the converter (not the non-existent 120 VAC inverter) to the solar charger in parallel with the PV panel(s). The reason is that the converter is a dumb, single stage charger that is not good for the battery. The solar charger is a smart, multi-stage charger with temperature compensation.

While at first glance this sounds like a reasonable plan, I have given up on it – not for any of the reasons mentioned but instead for reasons detailed in the links I listed in post nine.

[Larry,C]

I should know better than to come in late on a discussion and not read all of the previous posts. Please accept may apologies for any confusion or hard feeling that I may have created. I was just trying to keep anyone from making a mistake that would quickly discharge their batteries.

[gordon2]

Originally Posted by Larry,C

I should know better than to come in late on a discussion and not read all of the previous posts. Please accept may apologies for any confusion or hard feeling that I may have created. ...

No hard feelings here - just happy to be accurate.

[redbarron55]

I talked with the engineer at Bogart about using his charge controller exactly this way and his response was that they had not tested it but he could see no reason it would not work just like the solar supply except Tha for finish charging and bulk the "12 volt" supply might really have to be nearer 18 volts like a solar panel might be.
A few blocking diodes and a little more voltage might do he trick.

Sent from my SCH-I605 using Fiberglass RV mobile app